MEMORANDUM
To: J. Albertine, D. Helms, W. Skinner
cc: Division (M7), FEL Coordination Group
From: F. Dylla
Subject: IRFEL Weekly Report, February 17-21, 1997
Date: February 21, 1997
Management
Presentations for the DOE-BES Review scheduled for 23-25 Feb 97
were polished under the scrutiny of top Jefferson Lab management.
It was decided to defer all 10 MeV injector operations with electron
beam to the FEL Facility, and to concentrate activities in the
Injector Test Stand (ITS) toward maturing the technology for the
photocathode gun and establishing reliable operations of the gun.
Complete testing of the cryounit without electron beam will also
take place in the ITS as originally envisioned. Plans are to
move all gun and injector hardware to the FEL Facility starting
1 June. These injector activities preserve the milestone of installing
all hardware in the Facility by 30 Sep 97.
Injector Test Stand
Check out was completed on the hardware and software for the transverse/longitudinal
phase-space measurements in the beamline, calibrating the wire
scanners (harps) and magnets, and setting up the beam through
the downstream wire scanner (harp). Good extinction ratios were
also achieved of unwanted ghost pulses from the drive laser.
A power supply for the Personnel Safety System (PSS) failed, but
we recovered and recertified the PSS. Commissioning of the rf
kicker cavity for the longitudinal measurements continued, as
did commissioning of the spare 50 kW klystron.
Regarding upgrading the photocathode gun:
* Coated Cathode-Support Tube - The coated cathode support tube
was received from FM Technologies and is being prepared for electron-beam
welding.
* Ion-Implanted Ceramics - Lawrence Berkeley Laboratory modified
the rotisserie to enable continuous monitoring of the ceramic's
resistance during implantation. They subsequently commenced ion-implantation
of the second ceramic while, in parallel, diamond-scrubbing the
inadequate coating off of the first ceramic.
Regarding other ITS activities:
Commissioning was completed on the new resonant-ring fixture for testing warm ceramic windows, and testing of two windows followed. The tests included improved vacuum conditions and a new infrared imaging diagnostic supplied by NASA to monitor window heating. Unfortunately our vacuum interlock failed during the tests, resulting in a broken window. Subsequently we upgraded and tested the vacuum interlock, and we do not expect a repeat of this failure.
Additionally, we began developing a new window-test resource based
on using one of the 50 kW klystrons to supply rf power to the
window test fixture. This is expected to reduce the complexity
of the testing and provide a better model of the actual operating
conditions. It will also allow parallel testing of warm windows
in both the resonant ring and ITS cave. Warm windows are available
for testing.
Accelerator Systems
Regarding the beam-transport system:
The design of the reverse-bend dipole magnets continued, and the
back-check changes to the optical chicane dipoles were being done
at Northrop Grumman. The completed vellums of the latter, ready
for signature, are slated to be at Jefferson Lab on Wednesday
morning.
We attempted to glue mu-metal to the prototype dipole pole tips
with an epoxy system. The resulting gap was not satisfactory,
with .001-.002 inches lost to epoxy thickness. The correlated
variation in the field uniformity seen in magnetic measurement
of the result convinced us that this is an important parameter
and that we have to devote some development effort to it. The
magnet will now be used to test the influence of vacuum-chamber
welds on magnetic field. Plans are then to grind the mu-metal
pole tips flat and parallel to the contact surfaces of the back
legs and remeasure.
The prints for the differential pump station, back-leg girder
and injection-dipole girder are ready for signature. Layouts
of the stands for magnetic elements downstream of the cryomodule
were reviewed.
The first-article focusing quadrupole magnet passed its acceptance
tests. The stand for the prototype trim quadrupole was readied
for more detailed measurements. The prototype sextupole was assembled
and is now ready for measurement.
Regarding cryomodule fabrication:
A final internal review of the cryomodule design and existing
test results from the ITS cryounit was held on 19 Feb 97. No
show-stopping issues were identified. Responses to questions
are expected by 28 Feb 97, with close-out documentation eventually
to follow on www.
Regarding electron-beam diagnostics:
The beam-position monitor (BPM) contract was awarded with a delivery
date of 18 Apr 97.
Specifications for the power supply for the optical-chicane magnets
was reviewed and signed, and a purchase requisition was written.
First-article (assembly) printed circuit boards for the beamline
and gate-valve vacuum control cards were accepted. First-article
control cards for the ion pump power supply (IPPS) was tested
and accepted. Enough boards will be produced to replace all of
those boards in CEBAF for both the IPPS and gate valve controllers.
A leaky 6-way cross is holding up production of one of the beam
viewers. The cross is needed to support the beam-viewer assembly.
The vendor has purchased a new one and is machining it now.
Assembly and leak checking should be complete by Monday, with
shipment of 13 beam viewers by Feb 24th.
FEL Systems
Wiggler
Spectra technology has now measured and characterized a large
portion of the magnets required for the wiggler with the result
that all magnets measured lie well within the +/- 2% specification.
In fact all magnets measured to date lie within a +/- 1% variation.
This excellent performance will minimize the amount of trimming
needed to achieve the overall wiggler field quality specification.
Optics
Design efforts continued this week on the optical collimator.
The installation drawings for the optical transport pipe on the
ground floor are nearly complete. Several subassemblies (i.e.,
bases and stands) for the optical cavity were received and assembly
will commence in the coming weeks. The ion pumps were received,
along with other vacuum hardware.
Operations/Commissioning
The process of detailing specifications for the insertable dumps
(to be used in machine tune-up) and the scrapers began in earnest
with the goal of resolving engineering issues that surfaced at
the recent internal review of the IRFEL electron-beam dumps.
Detailed electron-tracking analyses suggest that the scrapers
may be completely unnecessary; deliberations are continuing on
this question.
A new procedure was developed for setting the momentum in the arcs using the air-core corrector magnets that are already part of the baseline design of the arcs. The procedure will soon be posted on www as part of the "arc 1 setup procedure".
Facility
The major effort this week was on framing the upper level of the
facility. By Friday the major frame steel was complete 3/4 of
the way down the facility permitting work to be planned for Saturday
in initiating joist installation in the East end. The lower level
floor was cleaned after flooding the previous week and several
actions taken to ensure that flooding cannot occur again. The
HVAC compressors were set on their pads and electrical hookup
of the main switchgear initiated. The contractor was sent a get-well
letter reminding them that there is a $ 1500/day penalty on not
achieveing beneficial occupancy of the second level by 3/15/97.
At present it appears that they are 2 weeks behind that schedule.